Kiersey Clemons‘ Jenn drags herself onto a remote island, shipwrecked and alone. She’s exhausted and traumatized, but resourceful, building shelter for herself and figuring out food and fire pretty quickly. But when night comes, she sees the silhouette of a massive beast walk on two spindly legs out of a deep recess in the ocean, storming onto the island, looking for food.

J.D. Dillard (Sleight) returns to both Sundance and Blumhouse with Sweetheart, the majority of which has Jenn battling solitude, starvation and a giant, terrifying monster in near-silence. It’s thrilling to watch a film that relies almost entirely on Clemons’ dazzling presence, and she has no trouble carrying the weight of her scenes alone, often with no dialogue. She gives such a wonderful, profoundly human performance, and watching Jenn figure out basic life necessities on this small, beautiful island would make for a compelling watch even without the monster.

But the monster is so cool, and we get a great look at it.

This isn’t a shaky-cam, shadowy sort of reveal, but an extended, close-up examination of a very well-designed and scary beast who’s used to ruling this island alone. Sweetheart is quite suspenseful even when it isn’t a full-on monster movie, but it doesn’t feel like much other horror we’ve seen. That’s in part because it’s so bright and gorgeous and thoughtful, and in part because the monster, as cool as it is, isn’t the most interesting part of this movie.

[Related] Read all of our Sundance reviews and coverage here!

That designation goes to Jenn, who’s probably the smartest and most composed shipwreck victim we’ve ever seen onscreen. From the moment she climbs ashore, Jenn is instantly in survival mode, surveying the island for resources that she will later use in a far cleverer way than we could have predicted. We’re always left guessing at her motives as she moves silently and determinedly across the island, and then when we see her schemes in action, we’re left with a deep appreciation of this character who has so much common sense and quiet, non-showy agency. Jenn is just, in a very straightforward and understated way, a boss.

Sweetheart loses its way a bit when it deviates from that perfect formula of Jenn surviving and fighting a monster on an island, but only because the film has presented such a compelling scenario that anything that isn’t that scenario feels like a loss. New characters are introduced mainly to give us more of a sense of who Jenn is and what she’s survived even before this catastrophe, but the truth is, Clemons’ eyes have already told us everything we need to know about Jenn. This is a woman who has regularly suffered disrespect, trauma and tragedy, and that makes her uniquely equipped to be on a deserted island confronting a prodigious deep sea monster that thinks of her as nothing more than meat. Jenn’s used to being underestimated. That’s her secret weapon.

Sweetheart is only 82 minutes and doesn’t waste a moment. It’s a beautiful and exhilarating film with an extraordinary leading performance and one hell of a big bad. Don’t miss it.